What depth do they run? Do you know? What pound line and diameter and type are the facts you have based on? Why would you use a 7? rod for deeper diving crank baits? What tools are available to help you answer any of these questions? Well the first suggestion I have is take the time to know and document the depth range of the crank baits you own in way that will serve you while on the water. Your electronics will tell you often where fish are located in a water column so knowing exactly what depth each crank bait you have runs will help you simply put a lure in that ?zone? which your electronics is giving clues.
The first suggestion is to use only one brand of crank baits. Pradco and more specifically the Excalibur and Bomber lines are a great line. Pradco has a yearly product guide that is a great resource it tells you exactly what each will do with a line weight associated with the reference. If you prefer another line I suggest saving all of your catalogues related to fishing tackle so you can reference that brand. Bass Pro Shops is an encyclopedia for all types of information, so save them for future reference. Take and mark the depth ranges with a magic marker on the top of the lid of your Plano boxes to have an on the water quick reference. The properties of some crank baits, are better suited for different types of cover. Square bill crank baits deflect better and work well in timber and wood cover. Tear drop shaped baits carry better in wind than do flat side baits but flat cranks have a wider wobble and create more disturbance in stained water and low light conditions. When using deep diving crank bait a little smaller is better because it drags less. You should own at least three crank bait rods or be able to change quickly on the water. One way to do that is use a duo snap on your crank bait rod so you do not have to tie constantly on the water.
Crank baits have an arch which is shaped much like the bottom of a boat from bow to stern. You need to understand this because it is the key to reaching your desired target under the water. Therefore, location of the lure is the secret to success in hitting the "zone". Here is an example…you see a brush pile in ten feet of water and you want to put a lure near this even bumping the brush pile. The cast must be made so that the baits downward arch reaches its peak before the target. Therefore the correct boat position and casting distance must be applied to ?hit the target?. When using deeper diving crank baits you need a longer rod and lighter line to help make longer cast and reduce drag from bigger line to get the bait in its effective zone. Also electronics have a small delay so what you see on the screen when moving is usually behind you so it is necessary to slow down, locate, and even mark the brush pile. Keep marker buoys on the front of the boat so when you get close to your desired target you can toss one near it. If it is deeper you can get the buoy a little closer but it is better to offset about ten feet so you do not spook fish and you do not catch the line from the buoy. It is a good idea to back off for a bit and fish near but not right on the cover to let it settle down a bit as well. Finally a good crank bait reel will help you to feel bites better as well as not work you as hard in getting the bait down to its effective zone.